Blackboard.



PATENTED JAN. 23, 1906.

T. H. COSTELLO.

BLAGKBOARD.

APPLICATION FILED AUG. 18, 1905.

will

UNITED STATES PATENT OFFICE. THOMAS H. COSTELLO, OF CHICAGO, ILLINOIS.

BLACKBOARD.

Specification of Letters Patent.

Patented Jan. 23, 1906.

To all whom, it may concern.-

Be it known that I, THOMAS H. COSTELLO, a citizen of the United States of America, and a resident of the city of Chicago, in the county of Cook and State of Illinois, have invented specification.

My invention relates to wall-blackboards for school and similar uses. Such boards usually consist of a foundation of some kind, upon the base of which is spread a proper pigment. The coloring-matter of such pigment consists of or is mingled with some elycomminuted abrasive material, by which the writing-surface is adapted to take the chalk or crayon. At one time the back or foundation for such boards was built on the walls of the school or other room when constructed, and being covered with black paint did permanent duty, (until the paint wore off) as well as gave the name by which this article of furniture, no matter of what material or color, is now known; but with modern developments in school furniture and fixtures the locally-constructed stationary boards have been superseded by those made by school-supply houses at business centers and by them shipped and distributed in quantities and otherwise as needed. Such boards heretofore have been practically rigid in their natural plane, and therefore cumbersome and inconvenient to handle. When made of fibrous material, as aper, they are more or less hygroscopic, and when fixed in place on a wall by the dampness thereof or of the atmosphere are caused to expand and buckle. When made, as they sometimes have been, to avoid the result of varying conditions of moisture, of vitreous material, they are too fragile to withstand the conditions and vicissitudes of a school-room.

It is the object of my invention to meet the conditions described by providing a completed blackboard, ready for mounting or attac ent to a wall, which will not bend or buckle by dampness or moisture, which cannot be broken or injured by rough usage, and which can readily be packed for shipment by rolling, if desired, so that large sections may be readily transported without danger of injury and at reduced rates of freight.

In the drawings illustrating'my invention, Figure 1 shows a blackboard in which several sheets of material are joined. Fig. 2 is a cross-section of the same, and Fig. 3 is a detail showing attaching means.

represent sections of blackboard mounted upon a wall and secured in place by nails or screws passing through the holes or slots B, slightly elongated for the purpose of providing against the slight expansion or contraction due to changes of temperature.

C is a frame or molding applied to the wall as a finish for the edges of the blackboardsection, and D represents the usual chalktrough at the bottom of the board.

The sections of blackboard material consist of a foundation a of very thin and flexible sheet metal. The face of this is covered with a layer of elastic pigment a, comprising a suitable abrasive material. The foundation of the section and the face thereof are greatly exaggerated in the drawings, representing, as they do, a verythin sheet of metal and a thin elastic pigment coating thereon. I prefer to make the body or foundation portion a of sections (which may be used separately or together, as shown) of steel, as this is less liable to injury by reason of its structural strength but the ordinary commercial sheet metal is objectionable, if not totally inapplicable, for

his purpose. Owing to inequalities of the rolls and variations of internal stress due to processes of manufacture, the sheets are more or less warped or twisted from a true level. A board of large size, therefore, will not lie close to the wall, and the uneven surfaces, though slight, provide varying angles at which the light may strike the surface, the work thereon being made indistinct and obscure to'the vision. WVhen, however, the inequalities of a sheet of steel have been eliminated, giving a perfectly flat and plane surface when extended, the' leveled material forms a foundationfitted to the present conditions of use and commercial distribution.

The coating with which the described foundation is covered should be elastic and strongly adherent to accommodate itself to any bending action of the foundation. It should consist of a proper elastic vehicle, to which should be added such materials as will give proper color and abrasive quality to the finished board. Such other material may also be added as may be useful in giving body to the compound and which at the same time may modify the color. These conditions may be fulfilled by many materials combined in different proportions, which will readily occur to those skilled in the art; but I suggest as combining the enumerated qualities the following composition: reboiled oil, one gallon; japan, one gallon; drier, one-half gallon; carbon black, twelve pounds; ground slate, ten pounds; emery or pumice, six pounds. To this may be added turpentine in sufficient quantity to make a mixture which will spread readily and smoothly. The color may be varied as desired by substituting chrome green or Venetian red for the carbon black, combining them or other pigments in such proportions as will produce the shade desired, due attention being given to the pigmentary effect of the other ingredients.

A blackboard level, hard, and indestructible. It is simple and easy of construction. It can be rolled and shipped in cylindrical form, thus greatly reducing the space required, the expense and labor of packing, and the cost of shipment and danger of injury while in transit.

made as described is ideally I claim and desire to secure by Letters Patent- 1. A blackboard comprising a flexible metallic foundation, and a flexible pigmented abrasive layer on the foundation.

2. In a blackboard a flexible metallic foundation having elongated openings for attaching the same, and a flexible pigmented abrasive layer on the foundation. 5

3. In a blackboard a foundation of flexible steel, and a flexible pigmented abrasive layer on the foundation. 1

4. In a blackboard a foundation of leveled flexible steel, and a flexible pigmented abrasive layer on the foundation.

In witness whereof I have hereunto subscribed my name, in the presence of two subscribing witnesses, this 16th day of August,

THOMAS II. COSTELLO.

Witnesses:

\ C. K. CHAMBERLAIN,

A. S. PHILLIPS. 

